This invention concerns skateboards, and especially wheel trucks supported beneath the skateboards on elastomeric bushings.
Skateboards have developed and evolved over the years. A relatively crude form of skateboard was available in the 1960s but did not achieve very wide use. The development of better wheel trucks and wheels, especially polyurethane wheels, brought skateboards much greater popularity, and in fact the development of these skateboard wheels led to better wheels on roller skates. The design of the skateboards, wheel trucks and suspension systems was continually improved, producing better steerability, agility and control in use of skateboards.
Elastomeric shock absorbing bushings have improved suspension, and also provided steerability. This type of mounting, shown in U.S. Pat. Nos. 6,105,978 and 6,739,603, has a base plate fixed to the bottom of the skateboard, with a threaded post extending down at an angle from the base plate. A wheel truck is secured to the threaded post in a sandwiched connection between two elastomeric bushings, one above and one below an opening in the wheel truck, tightened down by a nut on the threaded bolt or stud. A pivot point for steering is established by a pivot post that extends usually integrally from the wheel truck body into an elastomerically-lined bore or socket in the base plate, positioned about 1½″ or so from the threaded stud. Tipping of the skateboard platform, by shifting the weight of the user, rocks the wheel truck relative to the skateboard and causes a small turn angle of the wheel truck to occur relative to the skateboard platform, by swinging the wheel truck about the steering pivot point. Adjustments in stiffness can be made by tightening or loosening the nut on the threaded bolt or stud, or using elastomeric materials of different hardnesses.
U.S. Pat. No. 7,044,485 shows a modified form of the above-described wheel truck suspension, utilizing three discrete elastomeric bushing support points, one with a threaded post secured to a base plate as just described, and additional bushing seats at left and right, in a non-linear positional relation with the threaded bolt, upon which the metal wheel truck body rests. The outboard elastomeric supports are characterized as shock absorbers that can be interchanged for different response.